[llvm] [VPlan] Add transformation to narrow interleave groups. (PR #106441)

[Florian Hahn via llvm-commits]

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@@ -1555,3 +1591,129 @@ void VPlanTransforms::createInterleaveGroups(
       }
   }
 }
+
+static bool supportedLoad(VPWidenRecipe *R0, VPValue *V, unsigned Idx) {
+  if (auto *W = dyn_cast_or_null<VPWidenLoadRecipe>(V->getDefiningRecipe())) {
+    if (W->getMask())
+      return false;
+    return !W->getMask() && (R0->getOperand(0) == V || R0->getOperand(1) == V);
+  }
+
+  if (auto *IR = dyn_cast_or_null<VPInterleaveRecipe>(V->getDefiningRecipe())) {
+    return IR->getInterleaveGroup()->getFactor() ==
+               IR->getInterleaveGroup()->getNumMembers() &&
+           IR->getVPValue(Idx) == V;
+  }
+  return false;
+}
+
+/// Returns true of \p IR is a consecutive interleave group with \p VF members.
+static bool isConsecutiveInterleaveGroup(VPInterleaveRecipe *IR,
+                                         ElementCount VF) {
+  if (!IR)
+    return false;
+  auto IG = IR->getInterleaveGroup();
+  return IG->getFactor() == IG->getNumMembers() &&
+         IG->getNumMembers() == VF.getKnownMinValue();
+}
+
+bool VPlanTransforms::narrowInterleaveGroups(VPlan &Plan, ElementCount VF) {
+  using namespace llvm::VPlanPatternMatch;
+  if (VF.isScalable())
+    return false;
+
+  bool Changed = false;
+  SmallVector<VPInterleaveRecipe *> StoreGroups;
+  for (auto &R : make_early_inc_range(
+           *Plan.getVectorLoopRegion()->getEntryBasicBlock())) {
+    if (match(&R, m_BranchOnCount(m_VPValue(), m_VPValue())) ||
+        isa<VPCanonicalIVPHIRecipe>(&R))
+      continue;
+
+    // Bail out on recipes not supported at the moment:
+    //  * phi recipes other than the canonical induction
+    //  * recipes writing to memory except interleave groups
+    // Only support plans with a canonical induction phi.
+    if ((R.isPhi() && !isa<VPCanonicalIVPHIRecipe>(&R)) ||
+        (R.mayWriteToMemory() && !isa<VPInterleaveRecipe>(&R)))
+      return false;
+
+    auto *IR = dyn_cast<VPInterleaveRecipe>(&R);
+    if (!IR)
+      continue;
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fhahn wrote:

Simplified, thanks!

https://github.com/llvm/llvm-project/pull/106441